1. Field of the Invention
The present invention relates to an apparatus and method of printing images on both surfaces of a medium (such as paper). More particularly, the present invention relates to an apparatus and method for forming an image on a medium using a location change unit for locating a printing unit at any of first and second positions facing a first and second surface, respectively, of the medium.
2. Description of the Related Art
In a conventional method of forming an image using thermal transfer, a ribbon film is closely attached to media (such as paper) using a predetermined pressure, and ink coated on the ribbon film is heated using a thermal printing head (TPH), sublimated, and transferred toward the media. An example of a printer based on thermal transfer includes a printer disclosed in U.S. Patent Publication No. 20030071887, issued to Toshiyuki Yamamoto, the entire content of which is incorporated herein by reference.
A general ink ribbon as described above typically has a cassette shape. The cassette-shaped ink ribbon includes a feeding core around which a ribbon is wound, a winding core which winds the ribbon off the feeding core, and a housing which supports the feeding core and the winding core.
In an image forming apparatus using such an ink ribbon, for example, a color thermal transfer printer, the ink ribbon has a structure in which an arrangement of cyan (C), yellow (Y), magenta (M), and black (K) areas are repeated. Upon color image formation using this ink ribbon, each of the color areas of the ink ribbon should face a medium, and at least four coatings should be performed. To perform these coatings, sublimation and transfer of ink should occur while the medium is reciprocating four times.
As described above, in a conventional method of forming a color image, it takes a significant period of time to form an image, and requires a cassette for housing an ink ribbon. Since the media and the cassette are both consumption goods, they are economically burdensome to users. A mechanism for transferring and driving the media and the ink ribbon is also needed. Thus, an image forming apparatus becomes complicated and expensive.
Accordingly, a need exists for a printing unit which is capable of forming an image on a medium having first and second surfaces, with greater speed and requiring a simpler apparatus.